Dataset Information

Atmospheric oxygen regulation at low Proterozoic levels by incomplete oxidative weathering of sedimentary organic carbon.

ABSTRACT: It is unclear why atmospheric oxygen remained trapped at low levels for more than 1.5 billion years following the Paleoproterozoic Great Oxidation Event. Here, we use models for erosion, weathering and biogeochemical cycling to show that this can be explained by the tectonic recycling of previously accumulated sedimentary organic carbon, combined with the oxygen sensitivity of oxidative weathering. Our results indicate a strong negative feedback regime when atmospheric oxygen concentration is of order pO₂?0.1 PAL (present atmospheric level), but that stability is lost at pO₂<0.01 PAL. Within these limits, the carbonate carbon isotope (?¹³C) record becomes insensitive to changes in organic carbon burial rate, due to counterbalancing changes in the weathering of isotopically light organic carbon. This can explain the lack of secular trend in the Precambrian ?¹³C record, and reopens the possibility that increased biological productivity and resultant organic carbon burial drove the Great Oxidation Event.

SUBMITTER: Daines SJ

PROVIDER: S-EPMC5296660 | biostudies-literature | 2017 Feb

REPOSITORIES: biostudies-literature

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Atmospheric oxygen regulation at low Proterozoic levels by incomplete oxidative weathering of sedimentary organic carbon.

Daines Stuart J SJ Mills Benjamin J W BJ Lenton Timothy M TM

Nature communications 20170202

It is unclear why atmospheric oxygen remained trapped at low levels for more than 1.5 billion years following the Paleoproterozoic Great Oxidation Event. Here, we use models for erosion, weathering and biogeochemical cycling to show that this can be explained by the tectonic recycling of previously accumulated sedimentary organic carbon, combined with the oxygen sensitivity of oxidative weathering. Our results indicate a strong negative feedback regime when atmospheric oxygen concentration is of ...[more]

PMID: 28148950

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Project description:Most experimental studies measuring the effects of climate change on terrestrial C cycling have focused on processes that occur at relatively short time scales (up to a few years). However, climate-soil C interactions are influenced over much longer time scales by bioturbation and soil weathering affecting soil fertility, ecosystem productivity, and C storage. Elevated CO2can increase belowground C inputs and stimulate soil biota, potentially affecting bioturbation, and can decrease soil pH which could accelerate soil weathering rates. To determine whether we could resolve any changes in bioturbation or C storage, we investigated soil profiles collected from ambient and elevated-CO2plots at the Free-Air Carbon-Dioxide Enrichment (FACE) forest site at Oak Ridge National Laboratory after 11 years of 13C-depleted CO2 release. Profiles of organic carbon concentration, ?13C values, and activities of 137Cs, 210Pb, and 226Ra were measured to ?30 cm depth in replicated soil cores to evaluate the effects of elevated CO2 on these parameters. Bioturbation models based on fitting advection-diffusion equations to 137Cs and 210Pb profiles showed that ambient and elevated-CO2 plots had indistinguishable ranges of apparent biodiffusion constants, advection rates, and soil mixing times, although apparent biodiffusion constants and advection rates were larger for 137Cs than for 210Pb as is generally observed in soils. Temporal changes in profiles of ?13C values of soil organic carbon (SOC) suggest that addition of new SOC at depth was occurring at a faster rate than that implied by the net advection term of the bioturbation model. Ratios of (210Pb/226Ra) may indicate apparent soil mixing cells that are consistent with biological mechanisms, possibly earthworms and root proliferation, driving C addition and the mixing of soil between ?4 cm and ?18 cm depth. Burial of SOC by soil mixing processes could substantially increase the net long-term storage of soil C and should be incorporated in soil-atmosphere interaction models.

Dataset Information

Atmospheric oxygen regulation at low Proterozoic levels by incomplete oxidative weathering of sedimentary organic carbon.

Publications

Atmospheric oxygen regulation at low Proterozoic levels by incomplete oxidative weathering of sedimentary organic carbon.

Similar Datasets

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